1. Field of the Invention
This invention relates to the field of document processors for writing data to a document and reading data therefrom. The invention is especially useful as to an airline ticket and boarding pass printer and processor generally operable for issue of tickets and boarding passes and for receiving already-issued tickets and boarding passes for reading and verification, modification or reissue.
2. Prior Art
A wide variety of devices are known for producing a visually perceptible record in the form of printed characters or symbols. In addition to printing devices operable to print a visually-perceptible record on a document, the prior art includes special purpose printers operable to write corresponding records in a plurality of formats on a document, each format being intended for later use by specific document processing machines responsive to the particular formats used. In connection with ticket and boarding pass printers, and especially those used internationally, processing machines including optical character recognition devices (based upon strictly standardized character shapes), magnetic ink and/or magnetic strip reading and writing devices are known. It is usually necessary to have some visually perceptible data appear on the document for verification and sorting by humans. Disclosures particularly relating to tickets used for transportation can be found, for example, in U.S. Pat. Nos. 4,240,862--Ishiyama and 4,381,705--Roes, et al.
Specific ticket handling mechanisms are used in correction with airline ticket and boarding pass printers and also in connection with railway tickets. Railway tickets can be issued to riders with a certain number of rides or a certain sum of money encoded on the tickets as having been paid. The sum can be stored as a binary digital record on a magnetic strip and corresponding data is printed on the ticket such that the user can determine the current sum available. When the user presents the ticket in payment for a ride or like service, the recorded sum is read, reduced and written back to the ticket. By including more than one format, data is made available for use by machines and by humans, in a state most conveniently processed by them. Examples of multi-format tickets are found in U.S. Pat. Nos. 3,641,931--Hickox, et al; 4,040,345--Adams, et al; and, 4,196,665--Rogers, et al.
The need to process documents with multiple formats presents a challenge to the designer. Each format requires its own structure adapted for reading and writing apparatus associated therewith. These structures could routinely be laid out one after another, however, this multiplies the size and complexity of a device. Furthermore, record processing requirements can be inconsistent. Some formats (e.g., magnetic strip) require a continuous motion of the form while writing or reading. Other record processing steps (e.g., character printing with impact heads) are more difficult if the documents are allowed to move continuously relative to the processing apparatus. A typical approach to the problem of inconsistent requirements for the various different formats according to the prior art has been to use separated forms and to dispose each of the separate format processors at a different and distinct point along a transport path, sufficiently remote for different document handling parameters at separate areas along an elongated processing path. The result is a device which is relatively large, and characterized by complex feed characteristics.